Abstract Greenhouse studies were conducted to evaluate the effects of biosolids amendments on phosphorus (P) availability in two Florida pasture soils with medium to very high native P content. Three granular, anaerobically digested, heat-treated, exceptional quality biosolids (from Baltimore, MD, Tampa, FL, and Largo, FL), and a commercial fertilizer, concentrated super phosphate (CSP) were applied to A horizons of the two soils: the Millhopper sand [very high native P and oxalate extractable iron + aluminum (Fe + Al)] and the Candler sand (medium to high native P and oxalate extractable Fe + Al). After a four-month cropping season, bahiagrass (Paspalum notatum Flugge) yields did not vary with P-sources and application rates primarily because of the natively high soil-P. The effect of added P on P uptake by bahiagrass was minimal in the Millhopper soil, but significant in the Candler soil. The excessive native P and high P retention capacity of Millhopper soil masked the effect of P addition by the amend...